Automatic control



Oct. 25, 1949. B L 5M|TH AUTOMATIC CONTRAOL Filed Jan. r9, 1946 A 7- TORNE Y Patented Oct. 25, 1949 UNITI-:ZDY STATES PATENT GFFICE AUTOMATIC CONTROL Benjamin L. Smith., Gary, Ind.

Application January 9, 194:6,-Se'riafll No". 639g9`91 6 Claims.

Thisinventiorr. relates to`v` an automatic control andfrnore" particularly to al control for auton matically closing. the fuel valve of a soaking pit whenthe pit cover'i's' being lifted` and opening the fuel valvev when' the pit coveris placed over ther pit opening.y As isfwellfknownf, ingots are charged into the, combustion chamber of a soaking pit when; thepitcover is notv in place and after the in'gcts` are charged into the pit the cover is replaced; During'the-normal operation of the furnace the pitcover isA in place and the gas pressure in! the pit' i-s'keptconstant by means of an automatic control operated by the pit pressure which changes the position of the staclt damper as the pressure' varies;z In other words, ifv the pressure in the pit'v tends to rise, the stack damper autornaticallyl op`e'ns,and.l if the pressure decreases, thefstacli damper' automatically closes until the pressure becomes normal. When it is desired to remove the charge from the furnace, the cover is lifted andthe gas is turned off manually. This arrangement is unsatsifactory since there is no direct communication between the operator turning off the gasmanually at the control panel and the cover' crane operator. If the cover is lifted off before the gas is shut off, a heavy sheet' of names shoots high up into the air all aro-und the cover causing damage to equipment and endangering the lives of men working around the pits. Various attempts have been made to overcome thisobjectionable feature, but none have proved to be entirely satisfactory.

An object of this invention is to provide means for shutting off the fuel gas the moment the pit pressure drops to zero.

Another' -obj ect is to provide a device which will positively shut off the gas'as soon as the pit cover is vlifted ofl:` the pit.

These and other objects will be more apparent after referring to the following specification and attached drawings, in which:

The single' ligure shows a schematic wiring diagram hooked up to the stack damper.

Referring more particularly to the drawing, the reference numeral 2 indicates the fuel supply line leading to the combustion chamber 4 of a soaking pit or other article heating furnace. The pit is provided with an opening 5 and a cover 8 for closing the opening. A stack lf3 leads from the furnace and is provided with a stack damper l2 for controlling the flow of flue gas therefrom. A lever I4 attached to the damper shaft B6 is connectedA by means of an adjustable link i3 to a lever Zmounted on the shaft 22 which is rotated by means of a hydraulic cylinder 24 which is part ofthe furnace pressure-control. As shown in the drawing, the pressure regulator is actuated by the pit pressure through the conduit 25 to deliver fluid through either line 24a or 24D to the cylinder 24 to move the damper I2 one way or the other depending upon: Whether the`r pit pressure ils-above or below the pressure desired'. Thee'q-uipmerity so far described is not part of my invention, but'is the usual equipment used in' heating ingots.

lvfounteo'l:v on theI lever 201 is a standardmercoird switcnf'Zl which` consists of two'lconta'cts. 281' inserted. in a small glass tube which is closedfatone end: and contains a drop of mercury.v The. two contacts are mounted in a stopper'made of insulating` material fitted. into the opening end of a glass tube and projected a short distance intofthe tube.

The drawingfshows the position of thedamper and control' during normal operation of thefurnace; In this'position the mercury.- in theswitch -rowsagainst theV contacts 28 and; completes a circuit through the switch. The control circuit receives its power from the lines 3G, 32. In#V the lineA 3d isa normally closed contro'l'switch. 34 and a doublepole double throw switch 36,; In thefull line position shown in the drawinga switchv 36 completes' a circuit vto the rn'ercoid' switchy 2-6 through the'l-ines 3%; Lines 3S, 32 and 38 cornpletea c'ircuitto-a relay coil'4llwhich operates the relay switch 42 located: iny the. line 44;' Alsolocatediinf theliner44 is a'solenoidll for controlling the-operation of a gas valvev 'llocated` in the' fuel lin-e2.

The operation of the device is as follows'cl With the' furnace operating! normally the mercoid switch 26l willI be'inl such position thatthe contacts 28 will be closed; This completes the circuit to the-relay coil lltk throughy line 3); switch 34, double' throw switchv 353, line 38, lInercoid slr/itch 26, line 59 andline'SZ. This energizesrelay coill 46 causing relay switch 42' to close',l thus completingv a: circuit from line 3u to line' 32 through solenoid 46, line 44'and' switch 42'.A This energizessolenoidl; causing gas valve 48'to o'pen. When the cover is lifted from the furnace,` the pressure therein drops to zero, thus"v causing the furnace pressurel control to' close damperY l2; As thelever Zrotates to close damper l2; the' drop of mercury in the switch 25' flowsaway from the contacts breaking the circuit to coil' 40. This opens the switch 42, deenergizing solenoid 4t and closing. valve 48'. When the cover is placed over the pit opening', the' pressure immediately increases, th-us opening'the'stack damper and tilting the mercoidr switch 25 to' cause the mercury to flow toward the contacts. This'. completes the circuit-to relay coil land causes the valve 48 to open as hereinbefore described. f If the mercoid switch should. break or fail to function for any reasonitis advisable that the valve' 48 should be manually-controlled since otherwise' the charge would be overheated or otherwise damaged. In order to accomplish this, the double pole double throw switch 3&5 is moved to the dotted line position and the circuit is completed to the relay coil 3 4l) through the line 52. The opening and closing of valve 43 is then controlled by means of the switch 3e.

While one embodiment of my invention has been shown and described, it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims. f

I claim:

1. In an article heating furnace having a combustion chamber, means for delivering a uid fuel to said chamber, said chamber having an opening therein for charging articles thereto, means for closing said opening, a stack leading from said chamber, a damper in said stack for controlling the flow of flue gas therefrom, and means for opening and closing said damper, the improvement comprising a switch operable by movement of said damper, a valve for controlling the now of said fuel to the combustion chamber, and an electric circuit including said switch for opening said valve when the damper is open, the movement of said damper to its closed position changing the position of said switch to open said circuit and move said valve to closed position.

2. In an article heating furnace having a combustion chamber, means for delivering a fluid fuel to said chamber, said chamber having an opening therein for charging articles thereto, means for closing said opening, a sta-ck leading from said chamber, a damper in said stack for controlling the ow of flue gas therefrom, and means for opening and closing said damper, the improvement comprising a switch operable by movement of said damper, said switch being closed during normal operation of said furnace, a valve for controlling the flow of said fuel to the combustion chamber, and an electric circuit including said switch for opening said valve when the damper is open, the movement of said damper to its closed position opening said switch to open said circuit and move said valve to closed position.

3. In an article heating furnace having a combustion chamber, means for delivering a fluid fuel to said chamber, said chamber having an opening therein for charging articles thereto, means for closing said opening, a stack leading from said chamber, a damper in said stack for controlling the flow of flue gas therefrom, and means for opening and closing.r said damper, the improvement comprising a switch operable by movement of said damper, a valve for controlling the iiow of said fuel to the combustion chamber, an electric circuit including said switch for opening said valve when the damper is open, the movement of said damper to its closed position changing the position of said switch to open said circuit and move said valve to closed position, and a double throw switch in said circuit normally positioned to complete the circuit through the first named switch, said double throw switch being movable to by-pass the first named switch to permit manual control of said valve.

4. In an article heating furnace having a combustion chamber, means for delivering a' uid fuel to said chamber, said chamber having an opening therein for charging articles thereto, means for closing said opening, a stack leading from said chamber, a damper in said stack for controlling the flow of flue gas therefrom, and means for opening and closing said damper, the improvement comprising a switch operable by movement of said damper, said switch being closed during normal operation of said furnace, a valve for controlling the flow of said fuel to the combustion chamber, an electric circuit including said switch for opening said valve when the damper is open, the movement of said damper to its closed position opening said switch to open said circuit and move said valve to closed position, and a double throw switch in said circuit normally positioned to complete the circuit through the first named switch, said double throw switch being movable to by-pass the first named switch to permit manual control of said valve.

5. In an article heating furnace having a combustion chamber, means for delivering a fluid fuel to said chamber, said chamber having an opening therein for charging articles thereto, means for closing said opening, a stack leading from said chamber, a damper in said stack for controlling the flow of flue gas therefrom, and means for opening and closing said damper, the improvement comprising a solenoid controlled valve for controlling the flow of the fuel to the combustion chambenan electric circuit for energizing said solenoid to open said valve when the damper is open, and a mercury switch in said circuit operable by movement of said damper, said switch being closed during normal operation of said furnace, the movement of said damper to its closed position opening said switch to open said circuit and move said valve to closed position.

6. In an article heating furnace having a combustion chamber, means for delivering a, uid fuel to said chamber, said chamber having an opening therein for charging articles thereto, means for closing said opening, a stack leading from said chamber, a damper in said stack for controlling the flow of flue gas therefrom, and means for opening and closing said damper, the improvement comprising a solenoid controlled valve for controlling the flow of the fuel to the combustion chamber, an electric circuit for energizing said solenoid to open said valve when the damper is open, a mercury switch in said circuit operable by movement of said damper, said switch being closed during normal operation of said furnace, the movement of said damper to its closed position opening said switch to open Said circuit and move said valve to closed position, and a double throw switch in said circuit normally positioned to complete the circuit through the rst named switch, said double throw switch being movable to by-pass the rst named switch to permit manual control of said valve.

BENJAMIN L. SMITH.

REFERENCES CITED The following references are of record in the i'lle of this patent:

UNITED STATES PATENTS 

